''Burning'' Weapons Plutonium
in CANDU Reactors

~ verbatim excerpts from ~

Management and Disposition
of Excess Weapons Plutonium

Committee on International Security and Arms Control
U.S. National Academy of Sciences (1994)

Table of Contents

1. Who wrote this report, and why?

2. The Problem: Plutonium and Nuclear Weapons

3. Options for Storing Weapons Plutonium

4. Public Concerns About Plutonium ''MOX'' Fuel 5. Risks and Benefits of the CANDU Option 6. Toward a Plutonium-Free World

1. Who wrote this report, and why?

From ''Preface'', page v

With the end of the Cold War, the United States and the nations of the former Soviet Union are engaged in arms reductions on an unprecedented scale. What to do with the materials from the tens of thousands of nuclear weapons to be dismantled has become a pressing problem for international security.

This study results from a request to the National Academy of Sciences' Committee on International Security and Arms Control (CISAC) by General Brent Scowcroft, then the National Security Adviser to President Bush. Scowcroft asked for a full-scale study of the management and disposition options for plutonium after hearing a CISAC briefing on its discussions in March 1992 with a counterpart group from the Russian Academy of Sciences.

The Clinton administration confirmed CISAC's mandate in January 1993. The formal U.S. Government sponsor of the report is the Office of Nuclear Energy of the Department of Energy (DOE). . . .

CISAC's members include distinguished scientists, engineers, and policy experts. . . . John P. Holdren (Class of 1935 Professor of Energy, University of California-Berkeley) serves as chair, with Catherine McArdle Kelleher (Senior Fellow, the Brookings Institution) as vice-chair.

CISAC's former chair, Wolgang K. H. Panofsky (Professor and Director Emeritus, Stanford Linear Accelerator Center, Stanford University), chairs the plutonium study project. With the exception of Joshua Lederberg [nobel laureate in Chemistry], who was unable to participate in the project, all members of CISAC took part in the study and have unanimously endorsed the report. . . .

2. The Problem: Plutonium and Nuclear Weapons

From ''Executive Summary'', page 1

Many thousands of U.S. and Russian nuclear weapons are slated to be retired within the next decade. As a result, 50 or more metric tons of plutonium on each side are expected to become surplus to military needs. . . . Several kilograms of plutonium . . . are sufficient to make a nuclear weapon.

The existence of this surplus material constitutes a clear and present danger to national and international security. None of the options yet identified for managing this material can eliminate this danger; all they can do is reduce the risks.

Reactor-Grade Plutonium for Bombs?

From ''Introduction: Task and Context'', page 29

Several kilograms of separated weapons-grade plutonium and a somewhat larger amount of "reactor-grade" plutonium -- a minuscule fraction of the world stock -- would be enough to build a nuclear weapon. Thus, the plutonium in a truckload of spent fuel rods from a typical power reactor is enough for one or more nuclear weapons. The plutonium stored at a typical civilian reactor site or reprocessing plant is enough for hundreds of nuclear weapons.

From ''Introduction: Task and Context'', page 31

None of the policy options for managing the dismantlement of excess nuclear weapons and the storage and disposition of the resulting fissile materials [plutonium] can entirely eliminate the risks these items pose. Standards must be set by which to judge whether the remaining risks are acceptable. . . .

The high standards of security and accounting applied to storage of intact nuclear weapons should be maintained for these materials throughout these processes. . . . It may be institutionally difficult to preserve the strict security arrangements associated with nuclear weapons themselves. But precisely because of the difficulty of the task, it is important to preserve the goal.

From the Two-Page Spread :

Reactor-Grade and
Weapons-Grade Plutonium
in Nuclear Explosives

pages 32-33

Virtually any combination of plutonium isotopes . . . can be used to make a nuclear weapon. . . .

Use of reactor-grade plutonium complicates bomb design for several reasons. . . . Pre-initiation can substantially reduce the explosive yield, since the weapon may blow itself apart and thereby cut short the chain reaction that releases the energy. Calculations demonstrate, however, that even if pre-initiation occurs at the worst possible moment . . . the explosive yield of even a relatively simple device similar to the Nagasaki bomb would be of the order of one or a few kilotons.

While this yield is referred to as the "fizzle yield", a 1-kiloton bomb would still have a radius of destruction roughly one-third that of the Hiroshima weapon, making it a potentially fearsome explosive. . . . With a more sophisticated design, weapons can be built with reactor-grade plutonium that would be assured of having higher yields. . . .

In short, it would be quite possible for a potential proliferator to make a nuclear explosive from reactor-grade plutonium using a simple design that would be assured of having a yield in the range of one to a few kilotons, and more using an advanced design.

Theft of separated plutonium, whether weapons-grade or reactor-grade, would pose a grave security risk.

Harvesting Plutonium from Spent Fuel

From the Two-Page Spread :

How Accessible is
Plutonium in Spent Fuel?

pages 150-151

For countries with established military or commercial reprocessing [such as the U.S., Russia, the U.K., France, China, India, or Japan] the need to separate plutonium from spent fuel would pose effectively no barrier at all to recovering enough material for one or a few nuclear weapons, and recovering more would only be a matter of time and cost. Countries with such sophisticated nuclear technology, however, might choose to produce weapons-grade plutonium instead. . . .

For countries with no established reprocessing capability, recovering plutonium from spent fuel would be more difficult. All the essential processes are authoritatively described in the open literature, however, and the requisite technologies are available on the open market.

Indeed, rather than building the large and expensive facilities needed to separate plutonium on a commercial scale, a potential proliferator could rely on simple and relatively low-cost facilities, designed to separate enough plutonium for a few weapons, with little attention to safety and health.

Such a facility could in principle be built in an unexceptional warehouse-sized building. All the chemicals involved are widely available. . . . Significant engineering skill and experience would be required, however. The workers at such a simple facility would probably receive radiation doses large enough to increase their risk of cancer, but not to cause immediate illness. . . .

The IAEA's Standing Advisory Group on Safeguards Implementation has estimated that the time required to convert plutonium in spent fuel into a weapon would be one to three months, compared to seven to ten days for metallic plutonium. . . .

The proliferation risk posed by spent fuel grows with time, as its radioactivity becomes less intense. . . . After 15 years, the radioactivity declines by 50 percent every 30 years. How long it would take until remote [i.e. robotic] processing, the largest single obstacle to plutonium recovery, would no longer be needed, depends on how much radiation the workers in the facility would be willing to tolerate. . . .

3. Options for Storing Weapons Plutonium

Mixing Weapons Plutonium With Reactor Plutonium?

From ''Intermediate Storage: Forms of Plutonium for Storage'', page 120

Some Russian and U.S. officials have proposed blending excess weapons-grade plutonium with separated reactor-grade plutonium to create a material of intermediate grade for storage.

As described in Chapter 1, however, although the increased neutron background, heat and radioactivity from reactor-grade plutonium would complicate the job of making nuclear explosives from such a material, the reduction in proliferation risk would be small. . . .

Therefore this is not a promising approach to reducing the security risks posed by storage of weapons-grade plutonium.

''Burning'' Plutonium as MOX Fuel in Reactors?

From ''Long-Term Disposition: Minimized Accessibility Options'', page 154-5

A wide range of reactors -- existing, evolutionary, and advanced -- could use weapons plutonium in their fuel ... [but] a substantial fraction of plutonium would remain in the spent fuel.

The main goal of this approach is not so much to destroy the plutonium -- by fissioning the plutonium atoms or transmuting them into other elements -- as to contaminate it with highly radioactive fission products, requiring difficult processing before it could be used in weapons.

In addition, this option would shift the isotopic composition of the plutonium from "weapons-grade" toward "reactor-grade". As noted in Chapter 1, however, formidable explosives can still be made from reactor-grade plutonium. . . .

The quantity of plutonium remaining in the spent fuel would be substantial -- between 10 and 40 tons remaining from a disposition program beginning with 50 tons of weapons plutonium. . . . The specific destruction fraction [that is, the amount of plutonium actually destroyed] would have little impact on overall security risks. . . .

Vitrification of Plutonium with High-Level Waste?

From ''Long-Term Disposition: Vitrification'', page 188

In several countries . . . radioactive high-level waste (HLW) is to be mixed with molten glass in a process known as vitrification, producing highly radioactive glass "logs". . . . Ex-weapons plutonium could also be vitrified -- either with HLW, with other highly radioactive species, or in a glass bearing only the plutonium itself -- but this would add some technical uncertainties.

If plutonium were vitrified along with HLW . . . the glass logs produced would be resistant to theft by virtue of their large size and mass (the U.S. logs are to be some 2 meters long [and] weigh 2 tons), their high radioactivity levels, and the need for [robotically controlled] chemical separation to retrieve the plutonium. In addition, in both the United States and Russia, these logs are to be stored at major [secure] sites in the nuclear weapons complex, with accompanying physical security arrangements (which could be increased further if plutonium were added to the logs). . . .

The task of extracting the plutonium from the glass logs would be roughly comparable in difficulty to extraction of plutonium from spent fuel bundles, requiring a substantial remotely operated chemical processing capability. Moreover, experience with separating materials from such glass is far less widely disseminated than experience with spent fuel reprocessing.

Although the glass logs scheduled to be produced in planned U.S. HLW vitrification campaigns would be significantly less radioactive than fresh spent fuel (comparable instead to 50-year-old spent fuel), the canisters in which they would be emplaced would still emit doses of more than 5,000 rads per hour at the surface.

The plutonium in the logs would remain weapons-grade, rather than being isotopically shifted toward reactor-grade as in the case of the reactor options, but as noted in Chapter 1, nuclear explosives can be produced from either reactor-grade or weapons-grade plutonium. Thus, the committee judges that the plutonium in such glass would be approximately as inaccessible for weapons use as plutonium in commercial spent fuel -- particularly as in both the United States and Russia, the major vitrification operations are at nuclear weapons complex sites. with all the associated security.

From ''Long-Term Disposition: Vitrification'', page 190

It is extremely unlikely that a U.S. geologic repository will be ready to receive nuclear wastes of any kind before 2015. Consequently vitrified waste logs, with or without plutonium from weapons, will have to be stored in engineered facilities until a geologic repository is ready to receive them; with plutonium in the logs, safeguards would be required. The same is true, of course, for spent fuel from nuclear reactors.

4. Public Concerns About Plutonium ''MOX'' Fuel

Accidents, Waste, Health, Cost, & Public Acceptance

From ''Criteria for Comparing Options: Long Term Disposition'', page 83

[If weapons plutonium is used in MOX fuel for commercial power reactors,] particular attention needs to be given to the possible impacts of weapons plutonium use on reactor safety and on the disposal of the resulting nuclear waste. . . . [as well as to] the occupational risk from fuel fabrication -- where the far higher inhalation toxicity of plutonium per gram, compared to that of uranium, calls for special precautions that add significantly to the cost of [fuel] fabrication. . . .

In the case of use [of weapons plutonium] in reactors, public concern has rightly focused on the risk of reactor accidents. . . .

From ''Criteria for Comparing Options: Other Criteria'', page 84

In addition to the security, economic, and environmental, safety and health criteria just described, approaches to the management and disposition of excess weapons plutonium must be acceptable to both the public and the relevant institutions, and should, to the extent possible, avoid conflict with other policies and objectives.

Public Acceptability: Without public acceptance, successful implementation of any management and disposition approach is unlikely. Gaining public acceptance will require attention to environmental, safety and health protection, as described above, and encouraging a decision-making process with genuine public participation, both local and national. . . .

Security Needs Equivalent to Those for Intact A-Bombs

From ''Long-Term Disposition: Criteria for Disposal Options'', page 147

Risks of Handling: Nearly all disposition options . . . require processing and usually transportation of plutonium, in ways that could increase access to the material and complicate accounting for it, thus increasing the potential for diversion or theft.

In order to ensure that the overall process reduces net security risks, an agreed and stringent standards of security and accounting must be maintained throughout the disposition process, approximating as closely as practicable the security and accounting applied to intact nuclear weapons.

The Committee calls this the "stored weapon standard".

From ''Long-Term Disposition: Safeguards and Security'', page 163

The number of sites at which this plutonium is handled, the number of shipments of plutonium, and their length, should be minimized to the extent possible, to limit the risks of theft.

Plutonium Complicates Nuclear Waste Storage

From ''Long-Term Disposition: Environment, Safety and Health'', page 165

MOX spent fuel will contain more plutonium than typical spent fuel (raising potentially greater criticality concerns [e.g. an accidental nuclear chain reaction] after eventual emplacement in a geologic repository) and will emit more heat for a longer time (which has an impact on the repository volume required to hold a given number of fuel assemblies).

The possibility that the somewhat different chemistry of the MOX spent fuel would affect long-term release of radioactive materials in the repository would also have to be examined.

This different spent fuel would have to be separately licensed as an acceptable waste form for geologic disposal, meaning additional costs and potentially additional delays. . . .

5. Risks and Benefits of the CANDU Option

Political Uncertainty: Canadian Agreement Needed

From ''Long-Term Disposition: Canadian CANDU Reactors'', pages 173-175

Commercial heavy-water-moderated reactors in Canada, known as CANDU (for Canadian deuterium-uranium), appear to be capable, without physical modification, of handling 100 percent MOX cores . . . but major political questions remain open. . . .

All the pacing elements for plutonium disposition based on existing CANDU reactors would be the same as those for existing U.S. LWRs . . . except that there would be the added complication of seeking U.S.-Canadian agreement.

Advantages of the CANDU Option

The use of CANDU reactors has both advantages and disadvantages.

Advantages include:

Fewer Modifications for Plutonium Use:

Simplified Fuel Fabrication: No Reactor Shutdown Required for Spiking:

Disadvantages of the CANDU Option

The CANDU option also has important disadvantages:

Uncertain Canadian Acceptance:

Large-Scale International Plutonium Transport: Lower Radioactivity and Smaller Isotopic Changes:

Safeguards Issues of On-Line Refueling:

Other Difficulties with the CANDU Option

Approvals and Licenses.

Safeguards and Recoverability. Indirect Impact on Civilian Fuel Cycle Risks. Cost. Environment, Safety and Health.

Summary: Prospects for the CANDU Option


From ''Long-Term Disposition: Plutonium Transfers'', page 181

Russian plutonium might be shipped to Canada for use in CANDUs. . . . The risks of theft involved in the transatlantic shipment could be reduced to low levels if naval forces helped protect the shipment, but the controversies involved would be substantial. . . .

6. Toward a Plutonium-Free World

All Plutonium Poses a Grave Security Risk

From ''Long-Term Disposition: Beyond the Spent Fuel Standard'', page 205

Further steps should be taken to reduce the proliferation risks posed by all of the world's plutonium stocks, including plutonium in spent fuel.

It is time for the governments of the world to turn their attention to this problem again, to examine how nuclear power can best be managed to minimize these risks. That broad question is beyond the charge of this study. . . . Nevertheless, a few remarks are in order.

First . . . an improved international regime of safeguards and security for all separated plutonium . . . and ultimately for spent fuel as well, is required. The urgent problem of managing fissile materials from dismantled weapons should be used as the occasion for drawing the world's attention to building such a regime. . . .

In the longer term, further measures to limit human access to plutonium in spent fuel -- particularly older spent fuel -- are desirable. There are two main options available for this purpose:

Complete Elimination of All Plutonium

Complete elimination of plutonium has received considerable attention in debates over disposition of excess weapons plutonium. As noted above, the additional costs and complexities of the elimination options for excess weapons plutonium would be of little benefit unless also applied to other accessible plutonium, including the global stock of plutonium in spent fuel.

At the same time, in considering possible elimination options for that larger stock, it is essential to remember that as long as nuclear power is being produced by fission of U- 235 in fuels that also contain U-238, plutonium will continue to be produced. Thus until nuclear power in no longer produced in this way, there cannot be a plutonium-free world. . . .

[ The Dangers of Encouraging Plutonium Use ]
[ Bomb Makers Speak Out Against Plutonium ]

[ Plutonium Sub-Directory ] [ COMPLETE DIRECTORY ]


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